1. Field of the Invention
This invention relates to a LED lighting device having a plurality of reflectors of improved shape and disposition to sequentially reflect a substantial portion of the light emitted by the LED element to effect a lighting device having a large lighted surface. The enlarged lighted surface created by the current invention provides a more visible lighting device with a reduction in the hot spot characteristic of normal LED lamps.
2. Description of Prior Art
FIG. 21 shows a diagrammatic partial sectional view of a conventional prior art LED lamp C10. In FIG. 21 positive lead C1 is the positive lead wire. Contact wire C2 connects positive lead C1 to LED element C3. Negative lead C4 is the negative lead wire. Negative lead wire C4 has reflective cup C5 which partially surrounds LED element C3. LED body C6 is formed of a transparent resin which encapsulates LED element C3 and reflective cup C5. LED body C6 forms converging lens C7 which refracts and bends the light. If adequate electrical voltage is connected to positive lead wire C1 and negative lead wire C2 LED element C3 is energized to emit light. The emitted light forms a spatial radiation pattern. The light is moderately diverging and substantially centered about a pattern axis CA of the spatial radiation pattern.
A first portion of the emitted light proceeds directly through lens C7. A second portion of the emitted proceeds into concave reflective cup C5 whereat it is reflected and thereby redirected to also pass through concentrating lens C7. Both the first and second portions of light therefore are refracted at lens C7 to emerge concentrated about lamp body axis CX of LED lamp C10. Lamp body axis CX is the geometric axis of lamp body C6 and is coincident with pattern axis CA. Thus this prior art design of LED lamp C10 emits light concentrated about body axis CX of LED lamp C10.
For some uses concentration of the light about body axis CX is desirable. Other uses require the emerging light to be less concentrated. Refracting lens C7 can have a variety of shapes, however, it is not possible to reshape refractive surface C7 to effect the required divergence of the light for many uses. For these uses prior art designs employ a body C6 formed of a diffusing epoxyxe2x80x94usually milky whitexe2x80x94to encourage the divergence of the light about the pattern axis CA. This design is inefficient as light is absorbed and lost within the diffusing epoxy.
FIG. 22 is an end view of the FIG. 21 lamp as it would be seen by an observer along pattern axis CA. The size of the lamp as it appears to an observer is established by the size of LED body C6 which is usually small ranging up to 10 millimeters in diameter. This small size creates a hot spot with a high value of light energy per square millimeter leaving lens C7. This hot spot can be a problem as it impresses an image on a viewers eye which takes time to recede. It can also damage the viewers eye. The size of the lighted area can be increased by increasing the diameter of body C6. This however increases the mass and the cost of the device. It also can reduce the efficiency as light energy is lost passing through thick sections of the transparent resin.
The current invention employs an interior and an exterior reflector to sequentially reflect the light emitted by an LED element to create an efficient enlarged lighted surface LED lighting device. The current invention can be configured so that it comprises a large lighted surface even when the device is of limited mass and thickness.
The current invention initially efficiently spreads the light emitted by a LED element by providing an interior reflector of a size and disposition adequate to intersect the first portion and for some embodiments including a cup reflector both the first and the second portion of light emitted by the LED element. For the following discussion the light reflected can be the sum of the first and second portions previously described for prior art or it can be either the first or the second portion of the light. The interior reflector of the current invention is usually designed to bend the light away from a pattern axis of the emitted light. The interior reflector could alternatively be considered as designed to reflect the light to bring it towards parallelism with a reference plane normal to the pattern axis of the light emitted by the LED element. The interior reflective surface is usually disposed in close proximity to the LED element so that it can intercept a large percentage of the emitted light. The efficiency of the design can be maximized by locating the interior reflective surface sufficiently close to the LED element and by employing an interior reflective surface having an acceptable contour.
In one embodiment of the current invention the interior reflective surface is achieved by contouring the resin body which encapsulates the LED element such that the reflective nature of the interior reflective surface is the result of an internal reflection of the light. This embodiment is desirable because designing the resin body of the device to employ internal reflection usually minimizes the cost of the device. The interior reflective surface can alternatively also be achieved by coating a contoured surface of the resin body with a metallic coating. The interior reflector can alternatively be a discrete reflector attached to the LED element.
For some uses it is desirable that the light emitted by the lighting device substantially evenly illuminate a hemisphere centered about the LED element. For this requirement one embodiment of the current invention permits a percentage of the emitted light to pass through the interior reflective surface so that the light will not be totally reflected thereby avoiding dark zones within the hemisphere. This can be achieved by contouring the interior reflective surface to create internal reflection but not total internal reflection. In this embodiment a percentage of the emitted light is permitted to pass through the interior reflective surface to thereby distribute some of the emitted light within a hemisphere having the pattern axis of the emitted light as its axis. Alternatively, this result can be achieved by coating the interior reflective surface with a very thin coat of a metallic reflective coating thereby permitting a percentage of the emitted light to pass through the reflector to abet a more uniform distribution of emitted light within the hemisphere while reflecting a large portion of the emitted light to increase its divergence from the pattern axis. The light which passes through the reflective surface is refracted to form the required spectral radiation pattern of the light emerging from the lighting device. Finally, partial reflection can be achieved if the interior reflective surface is roughened or sanded. In this embodiment, the interior reflective surface will no longer have the smooth finish necessary for total internal reflection permitting some light to pass through.
Other uses require most of the light to be brought into a substantially parallel relationship with the pattern axis of the light. For these uses, an additional embodiment of the current invention employs a substantially parabolic contour on the interior reflector. This results in a concentration of the light about a plane normal to the pattern axis. A conical exterior reflector is provided to subsequently reflect the light to bring it towards parallelism with the pattern axis.
Finally, there are other requirements where the light must be bent away from the pattern axis to increase its divergence about the pattern axis into a user defined specific energy pattern about the pattern axis. These requirements are met with an embodiment of the current invention comprising a contouring of the exterior reflector to correspond to the contour of the interior reflector to distribute the light into the specific energy pattern required.
The interior reflector canxe2x80x94for some embodiments of the current inventionxe2x80x94be a discrete component attached to the LED element or to the body of the lighting device. However, usually the interior reflector is formed of the surface of the resin body which encapsulates the LED element. This design is desirable because forming the interior reflector from the resin body enhances the efficiency of the lighting device by minimizing the number of surfaces separating mediums of different indicies of refraction through which the light must pass before exiting the lighting device. Additionally forming the interior reflector of the resin body permits more accurate disposition of the reflector relative to the LED element thereby maximizing the accuracy of the redirection of the emitted light. Finally, this design is less expensive as it eliminates the need for a separate reflector which must be attached to the LED element. The exterior reflector to be later described can be similarly formed of the resin body of the device to further enhance the efficiency and reduce the cost of the device.
Subsequent to its reflection at the interior reflector an exterior reflector intersects and reflects the light. Usually the exterior reflector decreases the lights divergence about the pattern axis. Upon reflection at the exterior reflector the lightxe2x80x94depending upon a number of parametersxe2x80x94can emerge with a beam pattern similar to that of the light emerging from the prior art LED lamp of FIG. 21. There will be however substantial differences when viewed at a small distance such as distances of less than ten feet because the size of the lighted surface of the current invention will be larger than the lighted surface of the prior art FIG. 21 LED lamp. As a result of the large lighted surface the current invention will emit less energy per unit of surface area and thus be less prone to damaging a viewers eye. Finally, due to the limitations of the prior art lens C7 regarding refraction and its ability to collect a large percentage of emitted light the current invention which employs reflectors can project more of the light into a required beam pattern.
Although the current invention can be designed to emit light with a beam pattern having a divergence similar to that of prior art FIG. 21 while achieving the benefit of an enlarged lighted surface it also can be designed to achieve a second benefit of emitting light with an increased divergence about the pattern axis.
In addition to the interior and exterior reflectors, the current invention can additionally comprise a reflective cup similar to that previously described as reflective cup C5 of prior art FIG. 21. For this embodiment the light reflected by the interior reflector of the current invention includes the second portion of the light previously reflected by the reflective cup and identified as cup reflected light of prior art FIG. 21. This light will have been reflected three times prior to emerging from the current lighting device. Substantially all of the embodiments of the current invention shown herein function with or without the reflective cup.
It is an object of the current invention to sequently reflect light emitted by a LED element from an interior reflector with a lighted area or reflective surface of a first size to an exterior reflector with a lighted area or a reflective surface of a larger size. The light emerges from the lighting device from the large reflective surface of the exterior reflector making the lighting device more visible and less prone to effecting eye damage.
It is another object of the current invention to provide a LED lighting device which employs an interior reflector to reflect and bend the light emitted by its LED element such that as a result of reflection the parallelism between the light and a normal reference plane perpendicular to the pattern axis of the light as first emitted by the LED element is increased. Subsequently the reflected light is again reflected by an exterior reflector to decrease the parallelism between the light and the normal reference plane.
It is another objective of the current invention to contour and position an interior reflector to intersect light emitted from a LED element at acute angles of less than 40 degrees of its pattern axis to reflect that light to increase the divergence of that light about the pattern axis. Subsequently, the light is again reflected by an exterior reflector to decrease the divergence between the light and the pattern axis.
Another embodiment the current invention provides a LED lighting device whereby the light emitted by a LED element is subjected to at least two reflections such that at least fifty percent of the light emerging from the lighting device emerges within an angle of 30 degrees of the pattern axis of the light as first emitted by the LED element.
It is a further object of the current invention to provide a LED lighting device having an interior or first reflecting optic that reflects the light emitted by a LED element to thereby bend that light to bring that light towards parallelism with a normal plane disposed perpendicular to the pattern axis of the light as first emitted by the LED element. Further the interior optic at least partially establishes the contour of a hollow opening in the body of the lighting device thereby increasing the surface area of the body, increasing the conduction of heat away from the LED element and thus improving the survivability of the lighting device under excessive current or best conditions. The lighting device additionally comprises an exterior reflecting optic toxe2x80x94after the emitted lights reflection at the interior reflecting opticxe2x80x94intersect and reflect the light to bend the light towards the pattern axis.
It is a further object of this invention to provide a LED lighting device which is compact such that a group of the lighting devices can be arranged with each emitting light and with the light emitted by each experiencing minimal obstruction by other lighting devices in the group. Additionally, each of the lighting devices includes an interior reflector to direct its emitted light to bring that light towards parallelism with a common plane. An exterior reflector is also provided to at least partially surround or encircle the group such that common portions of the exterior reflector reflect the light from the group of lighting devices to effect a large lighted surface.
It is a further object of this invention to provide a LED lighting device having a large lighted surface. The lighting device is configured to additionally minimize its thickness normal to the lighted surface such that the lighting device can be employed within diminutive spaces.
It is a further object of this invention to provide a lighting device having a cup reflector to reflect the light emitted by a LED element into an interior reflector which subsequently reflects and directs the light into an exterior reflector which then reflects and directs the light to emerge from a large lighted surfacexe2x80x94the exterior reflectorxe2x80x94of the lighting device.